This is an interesting question, so it is gonna be long answer lmao

I believe Manny has the same curious and carefree personality that would make Luz a little less worried around people. For Emira this freedom has a bad taste because she might confuse it with Alador uncaring attitude. I think also she would be very doubtful with him for her own struggles with parents in general, until Amity goes and talks to her about how good person he is. So at some point idk, Emira (17) comes close and ask "tell, me, was it difficult for you to be a dad?" And a bunch of other questions that makes him truly worried of who raised those children 😭

I think Manny would be fond of her and Luz's friends in general, but this particular interaction makes him ask Luz to invite the Blight kids more often, to hang out, to dinner, anything to teach them how a real family feels like.
Adult Emira I think would view him as a reliable adult who she can trust to help her taking life decisions, and Manny thinks of her as a very responsible figure that need to disconnect from it every once in a while.